Portland State University. Department of Civil and Environmental Engineering
Date of Award
Master of Science (M.S.) in Civil & Environmental Engineering
Civil and Environmental Engineering
Structural analysis (Engineering), Buildings -- Strains and stresses -- Testing, Buildings -- Testing -- Technological innovations, Displacement sensors
Deflection measurements on structures, especially with regards to long-term monitoring, continues to be a challenge with current sensor technologies. Material degradation and changes in the mechanical properties due to aging (for example, creep and shrinkage in concrete bridges) directly impact the deflections exhibited by a structure. In this article we introduce and discuss the evaluation of a novel laser and video-based displacement sensor prototype to monitor displacements and rotations in structures remotely. The sensor is both inexpensive, using off-the shelf components, but also accurate and practical for situations that do not allow the use of conventional displacement sensors, which require a reference base. In contrast to other image-based approaches such as digital image correlation or Eulerian-based video sensors, our camera-based sensor is located at the measurement location on the structure. The sensor was evaluated using laboratory tests to determine the practicality, accuracy, and sensitivity to lighting conditions. The accuracy of the sensor was found to be approximately +/- 0.9 mm (95% confidence limits) for a 30.5 m (100 ft) measurement distance. Finally, we applied and evaluated the sensor under real-world conditions on a prestressed concrete bridge under different loading conditions as well as on a five-story steel moment-frame building under ambient conditions. Essential for field applications, the results demonstrate the prototype offers an inexpensive yet practical and accurate solution for monitoring displacements and rotations remotely.
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Brown, Nicholas J., "Evaluation of a Novel Remote Displacement Sensor Prototype Using Video and Laser-Based Technology for Civil Infrastructure Applications" (2019). Civil and Environmental Engineering Master's Project Reports. 49.